Question

If I have two iframes, how can I match the one that HAS NOT a youtube src ?

<iframe  src="http://googleads.g.doubleclick.net/pagead/ads?client=ca-feed-pub"></iframe>
<iframe  src="http://www.youtube.com/embed/Y4MnpzG5Sqc?wmode=opaque"></iframe>

Answer 1

You have all your data in a single string, that may contain several tags? In that case you’ll need to 1) find each separate iframe in string, 2) check each found iframe if you need to remove it or leave it alone. Here’s the code that does just that with comments showing where each step is performed:

var string='<iframe  src="http://googleads.g.doubleclick.net/pagead/ads?client=ca-feed-pub"></iframe><iframe  src="http://www.youtube.com/embed/Y4MnpzG5Sqc?wmode=opaque"></iframe><iframe  src="http://googleads.g.doubleclick.net/pagead/ads?client=ca-feed-pub"></iframe><some_good_tag>TEST</some_good_tag><iframe  src="http://www.youtube.com/embed/Y4MnpzG5Sqc?wmode=opaque"></iframe>'

function filter_iframe(iframe_tag){
    // if iframe have youtube in it - return it back unchanged
    if(/src=".+youtube/.test(iframe_tag)){ return iframe_tag }
    // if not - replace it with empty string, effectively removing it
    return ''
}

// first, find each iframe in string and call function to check if you need to remove it
var filtered=string.replace(/(<iframe.*?>.*?<\/iframe>)/g, filter_iframe)

console.log(filtered)